The heat exchangers generally comprise a stack of tubes or plates, for heat exchange, between a first fluid, such as a coolant, circulating in first channels of the stack of tubes or plates, and a second fluid, such as an air flow, for example flowing through second channels of the stack of tubes or plates.
The first channels for the first fluid, such as a coolant, must therefore be supplied with the first fluid.
For that purpose, thermal exchangers may comprise one or more openings fluidly communicating with a connecting device for connection to the first fluid circuit. In a known manner, a female part is realized on a metal component of the exchanger in the form of a sleeve surrounding the opening and is adapted to receive a complementary male part, such as a pipe or a tube, connected to the first fluid circuit.
According to a solution, heat exchangers can include a sleeve that is erected substantially perpendicularly with respect to the plane of the metal cover plate provided with the opening, in order to obtain a sufficient connecting face with the corresponding pipe or tube. Such sleeve is generally substantially cylindrical in the case of an approximately round opening. The corresponding male part is generally provided with a complementary cylindrical shape.
The pipe is inserted into and can later be brazed with the sleeve surrounding the opening. The sleeve and the pipe are generally concentric cylinders.
Further, it is known to introduce a brazing ring in the gap between the cylindrical pipe and sleeve. Then, during brazing, the brazing ring is melted and thus secures the connection.
The length of the gap for receiving the melted brazing material, in the direction of the longitudinal axis of the cylindrical sleeve and complementary pipe, is defined by the overlapping portions of both cylinders. In motor vehicles, a gap with an approximately 2.1 mm length in axial direction is requested by the constructors, for having proper brazing conditions in order to ensure a reliable connection between the sleeve and the complementary pipe of the connecting device.
However, with such a cylindrical connection, it has been noticed that the quality and distribution of the brazing material may not be stable. Indeed, those characteristics depend on the sleeve and pipe tolerances, on their position during the brazing and on tool precision.
Moreover, during brazing the temperature may not be homogeneous what can raises shrinkage cavities in the connecting device.
In order to provide adequate tightness between the male and female parts of the connecting device, according to a known solution, both female and male parts have been provided with complementary conical shapes with the same inclination, one of the male or female part can be pressed onto the inclined connecting surface of the complementary part thus eliminating every air gap between the male and female complementary parts of the connecting device.
However, with such a solution, a predetermined force has to be applied to ensure that the contact between both inclined surfaces is maintained during brazing.
Furthermore, such a configuration does not lead to optimal brazing conditions as required, in particular for motor vehicles, such as stability of a 2.1 mm length gap between both male and female parts, improving the quality and distribution of the brazing material, while ensuring temperature homogeneity during brazing.